Collapse of part of lung
I have gone through your query.
means collapse of lung resulting in absent gas exchange. Linear Atelectasis suggest that there is collapse of lung in a linear pattern. It is a very common finding in chest x-rays.
It can be caused by normal exhalation or due to some other causes like foreign body, mucus plug, smoking
, old age, blockage, tumors or tubercle.
Lingula is a part of lung and it scarring may be due to previous infection or inflammation.
Hope I have answered your query. If you have any further questions I will be happy to help.